Swivel assembly

Abstract

A multi-product swivel assembly for carrying oil or other cargo and transmitting electrical power and signal currents, between a ship and stationary oil wells or other installations. The swivel assembly includes a non-rotating or stationary unit, a large upper unit that rotates about the stationary unit, and a center unit that rotates with the upper unit and which extends down within the stationary unit. The center unit includes a large vertical cylinder which surrounds a group of vertical pipes carrying inflammable fluids, and a vertical pipe filled with inert gas and surrounding a conduit that carries an electrical cable. In order to repair the upper rotating unit, as to replace one of the muliple seals thereon, bolts can be loosened to separate it from the center rotating unit. When the bolts are loosened, a shoulder on the stationary unit prevents the center unit from dropping, so that during later reassembly, the bolts will lift up the center unit to its rotating position. To permit access to the bottom of the center rotating unit, jacking bolts are turned to allow the lower portion of the stationary unit to drop down until the seals and the like on the center unit are exposed, the stationary unit being lifted back into place by turning the jacking bolts.

What is claimed is: 
     
       1. A swivel assembly for lying in a body of water to transfer oil, natural gas, or other cargo to or from a ship or other floating structure comprising: a non-rotatable unit;   an upper unit surrounding the upper portion of said non-rotatable unit;   a center unit having a portion lying within said non-rotatable unit;   said upper unit having a top plate lying over said center unit, and said center unit having a top plate normally lying immediately under said upper unit top plate, said top plates having aligned holes;   a plurality of bolts extending through holes of said upper unit top plate and threadably engaged with holes of said center unit top plate; and   said non-rotatable unit having walls defining a shoulder for supporting said center unit against falling when disconnected from said upper unit, whereby unscrewing said bolts can gently lower the center unit onto the shoulder, while screwing in the bolts can raise the center unit off the shoulder.   
     
     
       2. The assembly described in claim 1 wherein: said shoulder is positioned at a height to support said center unit when it is lowered less than an inch from its fully raised position at which said bolts are fully tightened, whereby to provide enough clearance over the shoulder to avoid interference with normal rotation of the center unit, but permit the bolts to raise and lower the center unit with minimal turning of the bolts.   
     
     
       3. A swivel assembly for lying in a body of water, to transfer oil, natural gas, or other cargo to or from a ship or other floating structure, comprising: a non-rotatable unit having upper and lower parts;   a rotatable center unit having a lower portion lying within said non-rotatable unit, said center unit including a plurality of pipes extending largely vertically therein;   said lower part of said non-rotatable unit having a plurality of hose couplings, and a transfer coupler for transferring fluid between said pipes and said hose couplings;   a plurality of fluid seals vertically spaced from one another and disposed between said lower part of said center unit and said transfer coupling of said non-rotatable unit; and   a plurality of jacking screws rotatably mounted on said upper part of said non-rotatable unit and threadably engaged with the lower part of said non-rotatable unit, to permit the controlled lowering of said lower part to enable access to the seals.   
     
     
       4. The swivel assembly described in claim 3 including: a plurality of cables extending along one of said pipes of said center unit, said pipe carrying said cables extending down through said transfer coupler;   an electrical commutator assembly lying below said transfer coupling, including a body connected to said rotatable unit having a plurality of slip rings connected to said cables, and a plurality of brushes engaged with said slip rings and mounted on the lower part of said non-rotatable unit to move down therewith when the jacking screws are turned to lower them, to provide access to the brushes and to the slip rings and their cable connections.   
     
     
       5. A swivel assembly for lying in a body of water, to transfer oil, natural gas, or other cargo to or from a ship or other floating structure, comprising: a stationary unit having upper and lower portions;   a rotatable upper unit surrounding the upper portion of the stationary unit and rotatable thereon;   a rotatable center unit connected to the upper unit to rotate therewith, and extending vertically between the upper and lower portions of the stationary unit;   a plurality of pipes extending vertically along the center of the center unit;   a plurality of electrical conductors, said conductors extending along at least one of said pipes;   a transfer coupler lying at the lower portion of said stationary and center units, including a transfer block rotating with said center unit and a seal block closely surrounding said transfer block and having a plurality of axially spaced seals, at least one of said pipes that carries cables extending down through said transfer block; and   an electrical commutator assembly located below said transfer coupler and including a body rotatable with said center unit and carrying a plurality of vertically spaced slip rings coupled to said cables, and a casing mounted on said stationary unit and carrying a plurality of brushes engaged with said slip rings.   
     
     
       6. A swivel assembly for lying in a body of water, to transfer oil, natural gas, or other cargo to or from a ship or other floating structure, and to carry electrical power and signals therebetween, comprising: a stationary unit having upper and lower portions;   a rotatable upper unit surrounding the upper portion of the stationary unit and rotatable thereon; and   a rotatable center unit connected to the upper unit to rotate therewith, and extending vertically between the upper and lower portions of the stationary unit;   said center unit including a vertical cylinder, a plurality of vertical fluid-carrying pipes lying within said cylinder for carrying flammable fluids, a vertical cable-carrying pipe lying within said cylinder, a conduit pipe lying within said cable-carrying pipe, and at least one cable lying in said conduit pipe.